Other Assets Low-Income Housing Partnership (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jul. 31, 2010	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Company limited partner holding interest, percentage	99.90%
Tax Credits, reduction to income tax expense		$ 39	$ 29	$ 35
Unamortized investment balance classified as Other Assets		196	265
Maximum exposure to loss		$ 196	$ 265
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
General partner holding interest, percentage	0.10%